The invention relates to a coating device for coating composite pulp (cellulose) honeycomb support elements, each having a multiplicity of passages extending in an axial direction, with an impregnation coating for the purpose of increasing the fire and/or water resistance and/or the mechanical stability. The invention furthermore relates to a coating method for the purpose of coating such pulp sheets.
Composite honeycomb support elements are of known art, in particular when deployed as a honeycomb core material in composite sheets, wherein the honeycombs of the composite honeycomb support elements are formed from a multiplicity of passages extending in an axial direction, which as a rule are peripherally bounded by carrier papers, together with corrugated papers glued together with the carrier papers.
A method for the manufacture of composite honeycomb support elements is, for example, described in DE 103 05 747 A1. Other composite honeycomb support elements (corrugated box support elements) are shown in DE 196 54 672 A1 and DE 198 20 493 A1.
DE 20 2010 003 580 U1, DE 196 54 672 A 1 and WO 2008/076404 A2 are cited as further prior art.
From DE 36 31 185 A1 a method for the manufacture of composite paper honeycomb mouldings is of known art, in which a paper honeycomb element, i.e. a composite honeycomb support element with a multiplicity of axial passages, is coated with a curable fluid synthetic resin system. For the coating process the composite honeycomb support element is immersed in an immersion tank filled with the synthetic resin system, wherein the space above the immersion tank is evacuated. While the synthetic resin systems coming into use possibly increase the water resistance, they do not increase the fire resistance of the composite honeycomb support element. Moreover, large-scale use of the method of known art turns out to be difficult, because only a batch process can be undertaken. Also, with the method of known art the passages of the composite honeycomb support element cannot be coated with aqueous impregnation agents, since the paper honeycombs suck up the water and thereby lose strength; the honeycomb structure becomes soft and thereby disintegrates.
The applicant has overcome the disadvantages of the method of known art from DE 36 31 185 A1 with the method described in WO 2012/045653 A1. From the publication it is of known art to coat the composite pulp honeycomb support elements in a vacuum coating chamber with impregnation agent, wherein the impregnation agent is caused to swirl in the vacuum coating chamber. This method has proved itself. However, efforts are still being made to achieve simpler and more cost-effective coating options. In particular the throughput, i.e. the quantity of coated composite pulp honeycomb support elements per unit time, should be increased.
From WO 86/02039 a method for the manufacture of a light-build core is of known art, wherein the passages of the light-build core are formed from paper rolls. The axial passages are impregnated, in that impregnation resin, i.e. no inorganic impregnation agent, is filled in from above. As is described in the publication, a large quantity of impregnation resin remains adhered to the surfaces that are to be wetted. Excess resin runs out downwards. The coating device of known art does not operate continuously, but rather in batch mode, which is disadvantageous with regard to the coating rate. Moreover, the coating device and the coating method of known art are not suitable for coating with impregnation coatings containing cement, since these would clog up and/or soften the much thinner passages of corrugated board composite honeycomb support elements.
From WO 2008/094966 A1 it is of known art to coat a honeycomb structure with a material that can be thermally expanded (foam precursor). In a first variant of the method the honeycomb structure is transported along a “waterfall”, with which the passages are flooded with a foam precursor, which in turn is blown out using compressed air. Such a procedure is only possible with the foam coating material as described, which has a low density and a high viscosity. If a cement coating were to be used, the passages would inevitably clog up. In accordance with an alternative form of embodiment, the honeycomb structure is fixed in position and the “waterfall” with the foam precursor is moved relative to the honeycomb body. Here too a compressed gas is used for the purpose of blowing out the excess plastic coating material.
The methods of known art are not suitable for the purpose of coating composite pulp honeycomb support elements with an impregnation coating, in particular, an impregnation coating containing cement for the purpose of increasing the fire and water resistance, and/or the mechanical stability.
In addition reference is made to U.S. Pat. No. 5,462,623 and WO 2008/122616.